JP2729243B2 - Single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention supplies a raw material into a crucible according to the growth capacity of a single crystal pulled from the crucible, and continuously pulls a large-diameter and long-sized single crystal. Single crystal production method that enables

(Prior Art) As a single crystal production method, a so-called Czochralski (CZ) method, in which a seed crystal is immersed in a crucible, pulled up while rotating, and a single crystal is grown at the lower end of the seed crystal, has been widely known. Have been.

When attempting to obtain a large-diameter and long-sized single crystal in order to reduce the cost per chip by this method, the capacity of the crucible itself is limited, so that the raw material is placed on the melt surface in the crucible while pulling the single crystal. It is necessary to carry out so-called continuous pulling, and various methods have been tried in the past.

One of the methods is called a double crucible method.

Specifically, inside the crucible, another crucible having an opening for the flow of the melt or a cylindrical body is arranged, and the melt surface has an inner region for pulling the single crystal and an outer region for supplying the raw material. And the melt surface waves, dust,
This is a method for minimizing the influence of a temperature change or the like on the inner region which is a crystal growth region (for example,
57-183392, JP-A-47-10355, etc.).

In the conventional double crucible method, the melt consumed is simply detected, and a raw material corresponding to the consumed amount is supplied to the outer region and replenished.

For example, in Japanese Patent Application Laid-Open No. 63-95195, when the pulled single crystal has grown to a predetermined diameter (at the end point of the shoulder-making process), the weight sensor detects the increased pulling of the single crystal and converts the detection signal appropriately. The raw material is fed to the raw material charging device, and the raw material is replenished from the raw material charging device to the outer region.

(Problems to be Solved by the Invention) However, the conventional double crucible method often causes large diameter hunting in a single crystal.

FIG. 6 is a graph schematically showing a change in the liquid temperature of the inner and outer regions and a change in the diameter of the single crystal straight body (a so-called “body”) at the time of the occurrence of the diameter hunting. The hunting occurrence phenomenon will be described with reference to FIG. 6. When the raw material is supplied to the outer region under the condition that the liquid temperature in both the inner and outer regions and the diameter of the single crystal straight body are stable, the supply starts (at this point, FIG. among, the temperature of the outer region with the indicated at T _a) is a rapid drop.

After a few minutes, the temperature of the liquid in the inner region drops, and the diameter of the single crystal increases accordingly, causing a large-diameter hunting as shown in the figure. In some cases, the single crystal should be a dislocation-free single crystal. It will be dislocated. Of course, the diameter hunting causes a large loss when rounding the single crystal later.

Further, when the raw material is charged into the outer region, there is a problem that the melt in the inner region is solidified.

This will be specifically described using numerical values.
Assuming that the melt volume in the outer region is 10 kg, when pulling a 6-inch diameter single crystal at a pulling speed of 1.0 mm / min, the raw material must be supplied at 44 g / min. The melt temperature in the region drops by 15 ° C. Although the temperature of the melt is increased by the heater, solidification of the melt starts from the inner crucible edge in the inner region within a few minutes, and a situation occurs in which the melt cannot be pulled up substantially.

In order to avoid the above situation, it is conceivable to perform an operation to balance the material supply speed to the outer region and the melt temperature in the inner and outer regions before starting the pulling. It takes more than one hour for the time until the seed crystal is pulled down while pulling up the seed crystal, so-called seed drawing time, etc., and the above preparation time is not constant,
During this time, for example, a 6-inch single crystal with a pulling speed of 1.0 mm / mi
Even if n is 2.5 kg or more, the amount of the melt increases, and it is difficult to adjust the resistance of the single crystal to be pulled as a whole.

In the above-mentioned prior art, the double crucible method has been described as an example. However, the above-described problem is divided into a single crystal pulling region and a raw material supply region. This is a problem common to all devices in which a small-diameter melt passage is provided.

The present invention has been made for the purpose of proposing an appropriate raw material supply method under the above circumstances.

(Means and Actions for Solving the Problems) That is, the single crystal manufacturing method according to the present invention is provided with two regions for storing the melt, one of which is an inner region for pulling a single crystal, and the other is an inner region. Is a single crystal production method applied to an apparatus in which an outer region for supplying and melting a raw material is provided, and an opening through which a melt flows is provided between the two regions, wherein the raw material supplied to the outer region is provided. When increasing or decreasing the supply speed, the supply acceleration is ±
It is 6 × 10 ⁻⁵ / min ² or less.

Here, when the two regions are provided side by side, the region where the single crystal is pulled is the inner region according to the present invention,
The region for supplying the raw material is the outer region.

The reason why the above-mentioned supply acceleration includes minus is that the raw material supply speed is controlled so as to be reduced immediately before the end of the production of the single crystal of one lot, and the purpose is to include the supply deceleration amount in this case.

Then, the supply acceleration is ± 6 ×
The reason for setting it to 10 ^-5 / min ² or less is as follows.

Conventionally, the heater power was controlled in response to the increase in the amount of raw materials, but if the amount increases with acceleration,
Produces large diameter hunting. This is considered to be because the control effect of the heater power is delayed in time. Incidentally, heat propagation takes time (specifically, there is a “time constant” described later). Therefore, within the time constant,
The inventors of the present invention conducted an experiment to determine the relationship between the raw material supply acceleration and the diameter hunting amount in order to determine the "raw material supply acceleration that the heater power control effect can catch up with". Was.
The results are shown in FIG. From the experimental results, the present invention shows that the raw material supply acceleration is ± 6 ×
10 ^-5 / min ² or less.

(Operation) In the present invention, since the supply acceleration of the raw material with respect to the melt amount in the outer region is set to ± 6 × 10 ⁻⁵ / min ² or less, the effect of correcting the heater power before the heat is propagated to the inner region. It can be implemented, and as a result, large diameter hunting does not occur.

(Example) The present invention is implemented using an apparatus as shown in FIG.
In FIG. 5 (a), a container forming a hot zone, a heat retaining cylinder, a heater and the like are omitted.

In the figure, 1 is a single crystal being pulled, 2 is a funnel for supplying a granular material, 3 is a carbon crucible, and 4 is an outer crucible made of quartz. Reference numeral 5 denotes an inner crucible made of quartz. The inner crucible 5 is disposed inside the outer crucible 4 and at a concentric position, and is integrated with the outer crucible 4 by quartz welding or the like. Therefore, the melt in the crucible is separated into the outer melt a in the outer region A and the inner melt b in the inner region B by the inner crucible 5. A pipe-shaped passage 6 is provided as an opening through which the melt flows between the outer region A and the inner region B, and the pipe-shaped passage 6 is made of quartz and has a diameter of
It is variously selected in the range of 5 mm to 20 mm, and is provided near the bottom of the inner crucible 5. 6a is one port of the pipe-shaped passage 6 facing the outer region A (hereinafter, referred to as "melt intake port"), and 6b is the other port of the pipe-shaped passage 6 facing the inner region B (hereinafter, referred to as "melt intake port"). (Referred to as "melt outlet")
It is. Reference numeral 7 denotes a scattering prevention plate for preventing a raw material to be supplied into the outer region A from scattering and entering the inner region B.

First, control of a normal diameter, liquid temperature, pulling speed, and the like when no raw material is supplied will be described with reference to FIG.

The liquid temperature is controlled by increasing or decreasing the heater power so that the value of the radiometer 8 matches a preset profile.

That is, a normal carbon insulation tube surrounding the heater 9
The temperature of the part called 10 is measured with a radiometer 8, and more specifically, the value of the radiometer 8 when the seed crystal is placed in the inner melt b. The value of the radiometer 8 when expanding to a predetermined diameter after squeezing,
The heater power is controlled based on the value of the radiometer 8 at the time when the formation of the straight body portion (body portion) starts.

The lifting speed is also set in advance with a profile for the lifting length (accurately, the remaining liquid amount), and the lifting speed is controlled to match the profile.

However, the diameter of the single crystal 1 is not fixed even by the control of the liquid temperature and the pulling speed, and therefore, the above-described control of the liquid temperature and the pulling speed is corrected according to the actual change in the diameter of the single crystal 1. .

That is, it is dimensioned so that it can be moved in the horizontal direction.
The diameter of the single crystal 1 is measured by the CCD camera 11,
If it is detected by the CD camera 11 that the actual diameter of the single crystal 1 is larger than the expected diameter, the pulling speed is set within the range of the span width according to the preset profile. And the value of the radiometer 8 is simultaneously controlled so as to be higher than a preset profile within a preset correction amount range, so that the melt temperature is raised. Conversely, if the diameter of the single crystal 1 becomes smaller than the expected diameter, the reverse control operation is performed.

Next, the configuration of the raw material supply device 13 and control of the liquid temperature will be described with reference to FIG.

In the figure, reference numeral 14 denotes a raw material hopper, and a feeder 15 is provided below the raw material hopper 14. This feeder 15
Is an electromagnetic feeder type replenishment feeder 15a disposed directly below the raw material hopper 14, and an electromagnetic feeder type supply feeder 15b disposed below the replenishment feeder 15a.
And the supply feeder 15b is disposed on the measuring device 16.

Then, the granular raw material stored in the raw material hopper 14 is sent to the supply feeder 15b via the replenishment feeder 15a, and when the raw material on the supply feeder 15b reaches a predetermined amount, the measuring device 16 Upon detection, the supply of the raw material to the replenishment feeder 15a is stopped. On the other hand, a predetermined amount of the raw material on the supply feeder 15b is supplied to the outer region A by the funnel 2 in a predetermined pattern at an appropriate time for pulling the single crystal straight body portion (body portion).
The material supply pattern is set according to time.

By the supply of the raw material, the liquid surface position in the crucible fluctuates, and the melt temperature drops. Therefore, in the CZ method, the crucible height is controlled so as to keep the liquid surface position constant, and the heater power is controlled so as to keep the melt temperature constant.

Adjusting the crucible height to keep the liquid level constant (* The raw material supply amount is obtained by the measuring device 16). That is, the numerical value obtained by the measuring device 16 is processed by a computer, and the crucible height motor 12 shown in FIG. 2 is driven by the output signal obtained from the processed value to adjust the crucible height.

Prevention of a drop in the melt temperature is performed by correcting the profile of the heater power when no raw material is supplied.

That is, as shown in FIG. 4, the correction value of the radiometer 8 is proportional to the material supply speed, and this correction value is added to the heater power profile when there is no material supply and controlled.

As described above, the pulling speed, the melt temperature, the liquid surface position (crucible position), and the like when no raw material is supplied are profile-controlled in relation to the length of the pulled single crystal 1 (residual liquid). On the other hand, the feed rate of the raw material is profile-controlled in accordance with time, but is not related to the length (residual liquid) of the pulled single crystal 1.

Indeed, if the feed rate of the raw material is controlled according to the length (residual liquid) of the pulled single crystal 1, the amount of the pulled single crystal and the amount of the raw material to be supplied are always constant. , The pulling specific resistance is easy to control. However, when the feed rate of the raw material is controlled in accordance with the length (residual liquid) of the pulled single crystal 1 as described above, the following problem occurs when the diameter of the pulled single crystal 1 increases. Occurs. In other words, when the diameter of the pulled single crystal 1 becomes large, the pulling speed is increased to return the diameter to the original size. Is increased, the melt temperature is lowered, and as a result, the diameter of the single crystal 1 is further increased, and so-called diameter hunting is enlarged. For this reason, the feed rate of the raw material is not related to the length (residual liquid) of the pulled single crystal 1,
Profile control is performed according to time.

In this way, when the raw material supply rate is profile-controlled in accordance with time, particularly when supplied at a constant rate (g / min), there is no change in the amount of supply with respect to time. The advantage is that temperature fluctuations can be neglected. Therefore, the method of the present invention also basically employs a means of limiting the raw material supply rate in relation to time.

However, even when the supply speed of the raw material is controlled according to time, if the acceleration or deceleration until reaching the predetermined supply speed is too large, a large diameter hunting occurs.

Certainly, when the raw material is supplied, the above-described correction control of the melt temperature is performed, and theoretically, it should be possible to prevent the occurrence of diameter hunting by the correction control. However, in practice, there is a wasteful time of several minutes that is not reflected at all until the correction amount is reflected as an appropriate liquid temperature, and it takes 10 minutes to 20 minutes before the correction value appears as an effect on the liquid temperature. (The time required for the correction effect to appear) is usually referred to as “time constant”. The above-mentioned time constant always exists when the melt in the quartz crucible is heated by the heater, regardless of the control method.

Therefore, in the present invention, in order to suppress the diameter hunting during the supply of the raw material to a range (tolerable range) which is not different from the normal (when the raw material is not supplied) pulling hunting,
± 6 × 10 ⁻⁵ / m
in ² or less.

(Specific example) Using a crucible with the following specifications, the melt amount before starting the lifting is 25 kg for a 16-inch crucible and 35 kg for an 18-inch crucible.
, The amount of increase (correction value) of the heater power when supplying the raw material (granule raw material) is determined in advance, and the basic heater power is further increased to the melting point of the granule and the calorie required for the heat of fusion of the granule raw material The pulling operation of the single crystal is carried out at 1.2 times of that of the single crystal. The pulling speed and the melt temperature at the straight body (body part) of the single crystal are stable, and the diameter hunting of the single crystal having a diameter of 6 inches is ± When the raw material was supplied at a feed acceleration of 0.4 × 10 ^-5 / min at the time of 0.3 mm, the diameter hunting was ± 0.3 mm, which was the same as before the raw material was supplied, regardless of which crucible was used. Met.

◎ Crucible Specifications Outer crucible: 16 inches in diameter Inner crucible: 10 inches in diameter Outer crucible: 18 inches in diameter Inner crucible: 10 inches in diameter Outer crucible: 18 inches in diameter Inner crucible: 12 inches in diameter Outer crucible: 18 inches in diameter Inner crucible: 14 in diameter Inch *) The diameter of the pipe-shaped passage attached to the inner crucible is 10 inches.
パ イ プ 20 mm, and the length of the pipe-shaped passage is such that a melt of 5 times or more the weight of the single crystal pulled up per minute passes through in one minute.

(Effects of the Invention) As described above, according to the present invention, the diameter hunting is suppressed to a normal allowable size and, of course, dislocation does not occur. As a result, there is also an economic effect that no loss occurs in the rounding of the single crystal in the subsequent step.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a raw material supply method, FIG. 2 is a flowchart showing a control method of a melt temperature, a diameter of a single crystal and a pulling speed, FIG. 3 is a graph showing a relationship between a supply acceleration and a diameter hunting, FIG. 4 is a graph showing the relationship between the supply speed and the amount of correction of the radiation value, FIG. 5 (a) is a sectional view illustrating the structure of the crucible, FIG. 5 (b) is the same perspective view, and FIG. 4 is a graph schematically illustrating a change in melt temperature and a change in diameter hunting. A: outside area, B: inside area a ... outside melt, b ... inside melt 1 ... single crystal, 6 ... pipe-shaped passage

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Sakurada 1 in Higashihama-cho, Amagasaki-shi, Hyogo Osaka Titanium Manufacturing Co., Ltd. (72) Inventor Daizo Horie 1 in Higashihama-cho, Amagasaki-shi, Hyogo Prefecture 56) References JP-A-2-83292 (JP, A)

Claims (1)

(57) [Claims] 1. An apparatus according to claim 1, wherein two regions for storing the melt are partitioned, one of which is an inner region for pulling a single crystal, and the other is an outer region for supplying and melting a raw material. A method for producing a single crystal, which is applied to an apparatus provided with an opening through which a melt flows, the method comprising: Acceleration ± 6 × 10
^-5 / min ² or less.